What is a pansexual?

What is that? I had never heard of it before til the other day.

You may find the details in Wikipedia. As intriduction:

Pansexuality (sometimes referred to as omnisexuality[1]) is a sexual orientation characterized by the potential for aesthetic attraction, romantic love and/or sexual desire for people, regardless of their gender identity or biological sex. This includes potential attraction to people who do not fit into the gender binary of male/female implied by bisexual attraction. Pansexuality is sometimes described as the capacity to love a person romantically irrespective of gender. Some pansexuals also assert that gender and sex are meaningless to them. The word pansexual is derived from the Greek prefix pan-, meaning "all". This prefix is used specifically in contrast to the idea of 'two' genders as expressed by bi-, not to encompass all forms of sexuality, such as sexual fetishes unrelated to gender.

The adjective pansexual may also be applied to organizations or events. In this context, the term usually indicates an openness to the involvement of people of all genders and sexual orientations in said organization/event, not that everyone involved is, or should be, themselves pansexual. The terms "pansexual" and "bisexual" are not mutually exclusive terms, but rather pansexual is a way of defining bisexuality without necessarily denying the possibility of interest in genders and sexes such as those identifying as transgender or "genderf*ck."[2] The term alternatively is described as a "means to skip the binaries and existentialism of 'bi',"[3] and also criticized as being jargon-ridden and inaccessible.[4]

It means that you like everyone.